Threadbare
by Kato Molotov
Summary: [S7. Tumblr ficlet that accidentally found half a plot. Pure fluff.] Castle solves a long-forgotten domestic mystery and contemplates wormhole physics.


_Prompt: Caskett and Castle discovering that Beckett kept his red t-shirt, pretty please and thank you!_

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><p>It reappears one day, tucked inconspicuously near but not quite at the very bottom of his stack of old shirts. They're too worn for outside the house, but he keeps them for their soft warmth on lazy days in or nights when it's too cold to go to bed without clothing. At first he passes it over. It's obviously his. He's seen it a million times. Wondering why his old red shirt's presence suddenly niggles at the back of his mind, he gives a physical shrug to shake off the mental fog the item casts over him. It works, and Castle does not think about it again the entire day.<p>

It's the next morning that he realizes that it's not the shirt itself that bothers him. It's just a shirt, after all. What bothers him is that he cannot remember the last time he saw it.

He doesn't remember throwing it in the laundry. He doesn't remember putting it back. It's on top of his Doctor Who shirt, which Beckett has long since appropriated as pajamas or a makeshift coverup on the days they spend in varying states of nudity when the redheads make themselves scarce. It gets a fair amount of use. That should mean, logically, that the red shirt has been in recent circulation.

Except, as far as he can remember, it hasn't.

Castle's distraction follows him all the way to the dead body of the week - _dead guy in the park; must be Monday,_ he thinks absently - and leads him straight into Beckett's back, his feet clumsily trodding on the back of her boots and sending her toppling. His reflexes save her (and him) just in time, but he's earned himself a glare none the less, and the day does not particularly improve from that point on.

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><p>"Beckett," he begins, wary of the way his wife's eyes flash across the desk, "what do you think of the theory that lost items enter a rip in the space-time continuum, only to reappear in a slightly different place much later through another break, having spent all that time in a parallel universe?"<p>

"Does this have anything to do with our case, or have you been watching that Morgan Freeman thing again?" she raises one sculpted eyebrow.

"No, and yes, but—"

"Not my concern. Maybe the wormhole will take you to another dimension and drop you back here when you have something useful," Beckett snarks, with just a hint of her playful bite, enough to know that her earlier exasperation has (mostly) faded and that he's forgiven for almost tripping her onto a corpse.

Castle sighs theatrically. "Fiiinnee," he needles, standing and kissing her temple on his way out, "call me if we get something, but in the mean time, I'll head back home and start dinner. Alexis is bringing her mystery boyfriend around."

Beckett warns him, "Castle, if you do anything to the food…"

"Relax," he assures her, calling over his shoulder as he boards the elevator. "I'll wait until I get to know him to decide what kind of hazing he deserves!"

The doors close but he can picture her eyes rolling as clear as day.

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><p>He arrives home and does not start dinner. Instead, Castle drops his jacket in the front hall and heads directly to his closet. Staring at his ever-compressing section of the wardrobe, he takes inventory of his effects and finds that with just a little fuzziness around dates or occasions, he can remember the last time he wore each and every item.<p>

His summer clothes are put away, and twice-yearly, he purges and donates, so it's hardly been 4 months since he went through everything. All is accounted for, except that stupid, dark-red shirt, and he doesn't know why it's bothering him so much.

He worries about Alzheimer's until he remembers something he heard Terry Pratchett say at a con once, that Alzheimer's doesn't make you forget where you put your keys, but makes you stare at your keys and wonder what they go to. He thinks he's safe.

Pulling the shirt from the pile at last, Castle unfolds it for examination. It smells freshly-laundered, but immediately, his eyes go to the collar.

He did _not_ go over this shirt in his semi-annual purge. If he had, it'd have been tossed, because the collar is coming apart and the bottom hem has separated, and there are several small holes along the shoulder. Even for lounge clothes, this would have never made the cut.

Gathering it to his nose, he closes his eyes and finds it smells of Beckett in the way any person's oft-worn clothes smell of them, no matter how many washes.

The last time he saw it now comes to his mind fully and without effort.

He sees her shorter, darker hair swept into a messy knot, her face clean and fresh and nervous. He sees her scramble around the loft's kitchen, the first morning she ever did so, looking for this utensil or that to cook breakfast. He watches her disappear upstairs, appreciating the last view of her in his clothing, when they're called out to work the case again. And that was the last he saw of this shirt.

It's obvious that it's seen a great deal of use over the years since he last called it his. He pictures her wearing it.

He pictures her irritably throwing it on, on a day when she's been too busy with work to do laundry and has run out of other options. He pictures her putting it on over a long-sleeve thermal on an especially cold night, delighting in its extra warmth.

He pictures her stuffing it into the back of her closet and ignoring its existence for nearly a year. He pictures her bringing it back out for the first time on the night she arrives home from L.A. and goes home to an empty apartment, the memories of her dead partner and the what-ifs of them swirling in her mind, punctuated by a vague voicemail from Haiti.

He pictures her wearing it around her father's cabin, loose and baggy on her so as to not disturb her now-healed wounds. He pictures her crying into it after a drink with Scotland Yard and shoves the useless pang of guilt down his throat with a decisive swallow.

He pictures her nuzzling her nose into it and breathing it in the way she now does into his neck, on any nameless night they spent apart when they were just defining them. He pictures her taking it to D.C. and it making the ill-planned separation a little more bearable.

With a last, deep inhale of his own, Castle grins.

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><p>Alexis' new boyfriend is handsome, charming, successful, and talented.<p>

He is also Castle's second blast from the past of the day. A new haircut, a few years, and a taller-and-Beckett-reminds-him-older Alexis on his arm makes recognition difficult at first, but Martha's delighted crow of, 'Dylan! How lovely to see you again!' brings it all back to him.

Over dinner and a luxuriant Scotch, Dylan proves the perfect gentleman, and begrudgingly Castle admits his approval once the young couple have said their goodbyes for the night and Beckett's jab in his ribs is still sore from when he tried to object to the _for the night_ part.

"It's nice to see her date someone worthy of her time," Castle smiles faintly as he walks a half-sleepy Kate through the office, closing the door behind them and latching the newly-installed chain lock.

"So no hazing?" his wife teases, kicking off her shoes and beginning to undress - a show he stops and watches daily, no matter his other distractions.

Castle snorts. "No, there'll still be hazing. Castle family tradition. But I'll go easy on him." His arrival at this new plateau of maturity earns him a kiss, slowsweet and tinged with a bit of Scotch.

"Mmkay," she mumbles against his lips, looping her arms behind his neck.

Backing her toward their bed, Castle grins into her kiss. It's very rarely worth anything to interrupt where this is headed, but in this case? He thinks it's very worth it.

Fishing his red shirt from underneath his pillow, Castle breaks suddenly, watches Beckett's eyes struggle to focus and a bit of outrage conjure to her lips. (And what can he say? The woman is used to getting her way.) Her expression drops comically on sight of the garment in question.

"Look what the wormhole brought back! It's been missing for five years. Isn't that strange, Beckett?"

Kate snatches his old t-shirt from his grasp, bringing it to her chest and clutching it in a way that makes her attachment to it clear.

"Don't gloat, okay?" she mutters, fingering the soft material, the marks of four years of use that weren't there last he saw it, "I just…"

Her eyes are helpless and pleading but her mouth is set in a stubborn line, as if she's been momentarily transported somewhere else, back to when the ground was ever-shifting beneath their anxious feet. Maybe back to the year when their mutual deceptions almost ended them for good and yet the longing roiled just beneath their separate skins, every moment of every day. Her eyes cloud over and go unreadable. And how can he gloat, when she looks at him like that?

"No gloating," the author holds his hands up in a gesture of innocence, "it's sweet. It's sweet, Kate."

Beckett's quiet a moment longer, still touching the ragged edge of the collar when she returns his gaze, the opacity in her weary eyes gone and replaced with a sharp clarity, a glimmer of mischief.

"Oh, I don't think you'd say it's sweet if you knew what I did in this shirt."

She spends the rest of the night showing him how very _not_ sweet it was, but the morning comes and she's curled into his side, still wrapped in the t-shirt she borrowed and didn't return for five whole years. Which is fine by him. He never, ever wants her to give it back, anyway. Castle sweeps a lock of her hair away and whispers into her sleeping ear. He still thinks it's sweet.

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><p><em>Not my best, but hey, a sappy prompt delivers a sappy fic(let? How long is this thing anyway?)! Thanks for making me write stuff, Cami (<em>_drinkingcastleskoolaid)__!_


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